In the maintenance of energy efficient tightly constructed manufactured housing a large problem is presented during the cold winter months by the accumulation of living area humidity and excessive moisture, in the roof cavity above. This problem is caused by the accumulation of warm humid air in the living area some of which permeates and accumulates within the roof cavity. Moisture condensation and excessive humidity within the roof cavity reduces the efficiency of ceiling insulation which in time mats and compresses the insulation rendering the insulation ineffective. If cavity moisture buildup becomes too great, the ceiling below will sag and become water laden and water spotted and the exterior walls of the living areas will become wet and warped. Prior solutions to this problem include attempting to seal the roof cavity, but this is neither desirable nor practically possible due to migration of heat and moisture from the living quarters into the attic. Another prior solution has been to vent the attic only. This removes some moisture from the attic but does not affect the quality of the air in the living quarters. Also, with this system warm air is continuously removed from the attic during winter months to create a greater temperature gradient between the roof cavity and living quarters ceiling thereby increasing living area heating costs.